scholarly journals Estimating diet composition from scat analysis in otariid seals (Otariidae): is it reliable?

1988 ◽  
Vol 66 (8) ◽  
pp. 1865-1870 ◽  
Author(s):  
T. Dellinger ◽  
F. Trillmich
Keyword(s):  
Diet Composition ◽  
Clupea Harengus ◽  
Fish Length ◽  
South American ◽  
California Sea Lions ◽  
Scat Analysis ◽  
Sprattus Sprattus ◽  
Sea Lions ◽  
Fur Seals ◽  
Partial Digestion

Analysis of teleost sagittal otoliths contained in scats has been widely used to determine the diet of seals. This method is based on the assumption that relative frequencies of otoliths in scats faithfully reflect those offish in the diet. This assumption has rarely been tested experimentally. We compared the ratios of herring (Clupea harengus) to sprat (Sprattus sprattus) otoliths in faeces (output) of captive California sea lions (Zalophus californianus) and South American fur seals (Arctocephalus australis) with the ratios at feeding (input). Sea lions and fur seals showed no consistent differences in recovery rates and partial digestion of otoliths. Output ratios deviated only slightly from input ratios, the smaller sprat otoliths being underrepresented in the output by 8%. Only about 40% of the otoliths fed to the seals were found in the scats. For both species partial digestion of otoliths led to a 16% underestimation of fish length and a 35% underestimation of fish mass.

Species delimitation and nematode biodiversity: phylogenies rule

Nematology ◽  
2002 ◽  
Vol 4 (5) ◽  
pp. 615-625 ◽  
Author(s):  
Steven Nadler
Keyword(s):  
Species Delimitation ◽  
Sequence Data ◽  
Molecular Data ◽  
Gene Trees ◽  
California Sea Lions ◽  
Separate Species ◽  
Nucleotide Sequence Data ◽  
Sea Lions ◽  
Multiple Loci ◽  
Fur Seals

AbstractPractitioners of nematode taxonomy have rarely been explicit about what species represent or how data are being used to delimit species prior to their description. This lack of explicitness reflects the broader species problem common to all biology: there is no universally accepted idea of what species are and, as a consequence, scientists disagree on how to go about finding species in nature. However, like other biologists, nematologists seem to agree that species are real and discrete units in nature, and that they result from descent with modification. This evolutionary perspective provides a conceptual framework for nematologists to view species as independent evolutionary lineages, and provides approaches for their delimitation. Specifically, species may be delimited scientifically by methods that can test the hypothesis of lineage independence. For sequence data, such hypothesis testing should be based on sampling many individual organisms for multiple loci to avoid mistaking tokogeny and gene trees as evidence of species. Evolutionary approaches to analysing data and delimiting species avoid the inherent pitfalls in approaches that use all observed sequence differences to define species through calculation of a genetic distance. To illustrate evolutionary species delimitation, molecular data are used to test the hypothesis that hookworms parasitic in northern fur seals and in California sea lions represent separate species. The advantages and potential caveats of employing nucleotide sequence data for species delimitation are discussed, and the merits of evolutionary approaches are contrasted to inherent problems in similarity-based methods.

Individual variation in predation on fur seals by southern sea lions (Otaria byronia) in Peru

1993 ◽  
Vol 71 (9) ◽  
pp. 1908-1911 ◽  
Author(s):  
Robert Harcourt
Keyword(s):  
Adult Female ◽  
Individual Variation ◽  
Small Proportion ◽  
South American ◽  
Adult Males ◽  
Sea Lion ◽  
Subadult Male ◽  
Sea Lions ◽  
Hunting Success ◽  
Fur Seals

Southern sea lions (Otaria byronia) were observed to prey on juvenile and adult female South American fur seals (Arctocephalus australis) at Punta San Juan, Peru (15°22′S, 75°12′W) between October 1987 and December 1988. Over the course of the study there were 165 attacks on fur seals with 33 seals killed. While both adult male and subadult male sea lions captured and killed fur seals, adult female and juvenile sea lions never acted aggressively towards fur seals. Adult males attacked fur seals on 82.4% of the occasions when they were present at the rookery, subadults on 52% of occasions. Distinctive pelage characteristics allowed some of the male sea lions to be individually identified, and differences in hunting success were observed between adults and subadults, and between five identifiable adults who hunted on at least five occasions. Motivation for attacks differed for subadults and adults, with subadult males using captured fur seals as female sea lion substitutes, guarding them from others and copulating with them, whilst adult sea lions hunted fur seals as food. However, only a small proportion of adult sea lions hunted fur seals, and with differing rates of success.

scholarly journals Parasitological examination of northern elephant seal (Mirounga angustirostris) pups for presence of hookworms (Uncinaria spp.) on San Miguel Island, California

2016 ◽  
Vol 53 (2) ◽  
pp. 191-194
Author(s):  
E. T. Lyons ◽  
T. A. Kuzmina ◽  
T. R. Spraker ◽  
R. L. Delong
Keyword(s):  
Elephant Seal ◽  
Mirounga Angustirostris ◽  
California Sea Lions ◽  
Northern Elephant Seal ◽  
Parasitological Examination ◽  
Sea Lions ◽  
Fur Seals ◽  
Third Stage ◽  
Northern Fur Seals ◽  
San Miguel Island

SummaryNecropsy and extensive parasitological examination of dead northern elephant seal (NES) pups was done on San Miguel Island, California, in February, 2015. The main interest in the current study was to determine if hookworms were present in NESs on San Miguel Island where two hookworm species of the genus Uncinaria are known to be present - Uncinaria lyonsi in California sea lions and Uncinaria lucasi in northern fur seals. Hookworms were not detected in any of the NESs examined: stomachs or intestines of 16 pups, blubber of 13 pups and blubber of one bull. The results obtained in the present study of NESs on San Miguel Island plus similar finding on Año Nuevo State Reserve and The Marine Mammal Center provide strong indication that NES are not appropriate hosts for Uncinaria spp. Hookworm free-living third stage larvae, developed from eggs of California sea lions and northern fur seals, were recovered from sand. It seems that at this time, further search for hookworms in NESs would be nonproductive.

scholarly journals Impact of the 2015 El Niño-Southern Oscillation on the Abundance and Foraging Habits of Guadalupe Fur Seals and California Sea Lions from the San Benito Archipelago, Mexico

PLoS ONE ◽  
2016 ◽  
Vol 11 (5) ◽  
pp. e0155034 ◽  
Author(s):  
Fernando R. Elorriaga-Verplancken ◽  
Gema E. Sierra-Rodríguez ◽  
Hiram Rosales-Nanduca ◽  
Karina Acevedo-Whitehouse ◽  
Julieta Sandoval-Sierra
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
California Sea Lions ◽  
Sea Lions ◽  
Fur Seals

Inter-Specific Infanticide in South American Otariids

Behaviour ◽  
1998 ◽  
Vol 135 (8) ◽  
pp. 1005-1012 ◽  
Author(s):  
Marcelo Cassini
Keyword(s):  
Breeding Season ◽  
Active Role ◽  
South American ◽  
Sexual Competition ◽  
Sea Lions ◽  
Fur Seals

AbstractSouth American fur seals Arctocephalus australis and South American sea lions Otaria fiavescens breed sympatrically on several islands of the coast of Uruguay. O. fiavescens males will sometimes attack A. australis pups and shake or toss them for several minuh:s or even hours. These attacks may result in the death of the pup. I recorded 31 pup attacks at Rasa island, Uruguay, during 1996 breeding season. Most abductors were subadults, which frequently engaged in aggressive encounters with each other during the abduction. After these encounters, the largest males always retained the pups. Forty percent of the pups died during the attacks, which normally ended when the abductor abandoned the pup. Abductors did not mount or eat the pups. Attacks by Otaria males did not appear to have the function of killing Arctocephalus pups. Instead, inter-specific infanticide appeared to be a by-product of intra-sexual competition or sexual frustration of subadult males. The mothers attempted to recover the pup in 31% of the attacks. However, only one mother was able to get her pup away from the abductor. This active role of the mothers was not observed in other colonies where Otaria subadults also attack Arctocephalus pups, e.g. in Peru. This difference is probably associated with the fact that in Uruguay both species use the same islands for reproduction, while in Peru they reproduce allopatrically.

scholarly journals Helminth and respiratory mite lesions in Pinnipeds from Punta San Juan, Peru

2018 ◽  
Vol 63 (4) ◽  
pp. 839-844 ◽  
Author(s):  
Mauricio Seguel ◽  
Karla Calderón ◽  
Kathleen Colegrove ◽  
Michael Adkesson ◽  
Susana Cárdenas-Alayza ◽  
...  
Keyword(s):  
Parasitic Infections ◽  
San Juan ◽  
South American ◽  
Sea Lions ◽  
Fur Seals ◽  
Contracaecum Osculatum ◽  
Tissue Alterations

Abstract The tissues and parasites collected from Peruvian fur seals (Arctocephalus australis) and South American sea lions (Otaria byronia) found dead at Punta San Juan, Peru were examined. The respiratory mite, Orthohalarachne attenuata infected 3 out of 32 examined fur seals and 3 out of 8 examined sea lions, however caused moderate to severe lymphohistiocytic pharyngitis only in fur seals. Hookworms, Uncinaria sp, infected 6 of the 32 examined fur seals causing variable degrees of hemorrhagic and eosinophilic enteritis. This parasite caused the death of 2 of these pups. In fur seals and sea lions, Corynosoma australe and Contracaecum osculatum were not associated with significant tissue alterations in the intestine and stomach respectively. Respiratory mites and hookworms have the potential to cause disease and mortality among fur seals, while parasitic infections do not impact significatively the health of sea lions at Punta San Juan, Peru.

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